torture: Add rcu_normal and rcu_expedited runs to torture.sh

Currently, the rcupdate.rcu_normal and rcupdate.rcu_expedited kernel
boot parameters are not regularly tested.  The potential addition of
polled expedited grace-period APIs increases the amount of code that is
affected by these kernel boot parameters.  This commit therefore adds a
"--do-rt" argument to torture.sh to exercise these kernel-boot options.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>